This invention relates to paper shredders and provides a device for protecting the paper cutters of the shredder from damage.
Prior art paper shredders have a chute for guiding the paper to be shredded between two sets of cutting blades. In one type of shredding machine each set of cutting blades comprises a large number of thin discs on a common shaft. The discs are very small and the peripheries of the discs are the cutting blades. More details of two such machines are shown in U.S. Pat. No. 4,426,044 to Butler granted Jan. 17, 1984, and entitled "Document Shredding Machines," and U.S. Pat. No. 4,018,392 granted to Wagner on Apr. 19, 1977 and entitled "Shredding Machines."
When the paper that is fed into the cutting blades has a metal element such as a paper clip or staple, the delicate cutting blades of the shredder are damaged and must be replaced. The cost of such a repair usually runs to about $1300.
U.S. Pat. No. 4,354,178 teaches a metal detector for detecting small metal objects in wool before the wool enters a carding machine.